Trends in Mycobacterium tuberculosis resistance, Pakistan, 1990-2007

Objective: To determine resistance trends including the emergence of extensive drug resistance (XDR) in Mycobacterium tuberculosis (MTB) isolates from Pakistan. Methods: This was a retrospective analysis of MTB isolates (January 1990-June 2007) collected from the four provinces of Pakistan. Standard methods were used to isolate MTB. Susceptibility against rifampin, isoniazid, streptomycin, ethambutol, ethionamide, capreomycin, cycloserine, and ciprofloxacin was tested using the agar proportion method, while susceptibility to pyrazinamide was determined using BACTEC. Resistance over the study period was assessed using Chi-square for trend analysis. Results: Resistance in 15 343 MTB isolates showed a steady increase over the study period; a significant trend of increasing resistance was noted in three of the four provinces included in the study. XDR-tuberculosis was first seen in 1998; to date 22 XDR cases have been documented. MTB resistance was significantly lower (p < 0.001) in patients under 5 and over 60 years of age, and significantly higher in males than females (p < 0.001). MTB resistance was also higher in pulmonary than extrapulmonary isolates (p < 0.001). Conclusion: This study documenting a steady increase in resistance among MTB isolates and the emergence of XDR strains is concerning. The data highlight the need to ensure adequate treatment of cases in order to prevent a further increase in multidrug resistance within the country. The importance of developing systems for monitoring drug resistance through nationwide surveillance is emphasized.